Automatic positive stop and dwell arrangement for machine tools



3 Sheets-Sheet 1 .2706 022i- E67 R Grzmbwy, #fiefzi/fyf zzderaorz,

WW a z? I B. R. GRANBERG ET AL AUTOMATIC POSITIVE STOP AND DWELLARRANGEMENT FOR MACHINE TOOLS Flled Oct 7 1948 B. R. GRANBERG ETALAUTOMATIC POSITIVE STOP AND DWELL ARRANGEMENT FOR MACHINE TOOLS Aug. 15;1950 Flled Oct 1948 ."B. R. GRANBERG ETAL 2,519,042 AUTOMATIC POSITIVESTOP AND DWELL Aug. 15, 1950 ARRANGEMENT FOR MACHINE TOOLS I sSheets-She't 5 Filed Oct. 7, 1948 72% je7ZZZ %wr WM W awe;

Patented Aug. 15; 1950 AU'roMATro POSITIVE STOP AND DWELL "ARRANGEMENTFOR MACHINE TOOLS" .Biigt n. .Gramire and Bertil '1}. An er en, Rack;

' ford, 111;, assig'nors to $und strandMach ine Tool, I I fCo),Rockford, Ill., a corporation of Illinois."

I Q "Appiic'a'itnibatttr 7, 1948, Serial No.5;212 J i --'Ihi$ imamrelates e u t qh h tools, and moreparticularly-to an electrical: controlsystem foiga machine tool having. av,movable carriage including novelmeans providing automatic positiyestop and dwell of said carriage atraverse motor, and difierential drive meansfor driving a carriagewherein the traversemotor is braked during feed operation and automaticmeans e o d pe ti be ore t e..- riage engages a positive stop forreducing the bra-king torque on the traverse motorso that said :brake.will slip when, the; table strikes the .DQ i VQ QD- 1 ,;;sAnotherqobject is to'providean improved; con; trol system wherein fullbraking; torquezis-applied to ,thetraverse. motor: at the initiation ofthe feed portion of the cycle, but beforewthe carriage engages-a.positivejstop the t0rque,-:is automatically reduced so thatthebrakewill slip when .the carriage strikes thei'positive stop, thereduced torque being-highenoughto prevent the feed, motor from drivingthe :traverse motor the? fore the carriage engagesythe stop w furtherobjectv is; to provide improved lineans wherebythe amounmof braking:torqliemaybe readily ad'justedi to provide thatwsaid reduced torque ishigh enough to prevent rotationofrthe traverse motor-;-and: insurev feedmovement-1." of

saidcarriage, but lowa-enough to. permit zthe and'driving-motor. andgearing 'thereforladapted toqbev controlled by .an yelectrical -contr'olisystem herein disclfosedj 1 y. 3.. F Fig. 2 ma diagrammatic'view'zofan, electrical control:system;5including -in one embodiment the ea ur soithisinv n o x :1;

g-:3 diag mm iewe a lec ca font l t m inc dinsin an r mbo i nt the eaures e ithis nven i n-x 1 a a while 1t in ention isrsusceptible 0f; v ioificatipns; alternative;,constructiOnS; it is here shown and will bedescribedhereinafterin two; embodiments, It is not intended, however;

that the invention is to bejlimited tothe specific forms disclosed, buton theicontrary, it is intend; ed to cover all modificationsandalternative con-1 structions falling within the spirit and scope oi theinvention as defined-by the appended claims,

Though the invention may be embodie'din a variety of machine tools, itis for purposesof disclosure, illustrated, in the drawings and willhereinafter be desoribedas embodied in a milling machine, byway ofexample, a mach-inesimilar to that described in the patent to BengtRQGran berg, No.;2,203,298 dated ,lune 4, 1940. A ma chineofthatcharacter, has a base or bed frag: mentarilyshown at 10 in Fig. lupon which.;a. work supporting. carriage for', table li is. reciprocable; in ways Qf' CQl'lYQIlfiiGHEl] ,construction Such. a machinealsorhas a -tool support, .usually in the form ,of a spindle.lIn'asmuch,howeveiflljas the spindle or its control apparatus .Iorm'nopart of this invention, no disclosure thereof] isiiiade n liei J a 1 4is welliknown tothoseskilledin the art ,.,the carriageHIis usuallyreciprocated through a cycle includingvarious combinations ofiapid ortrav erse movements and feed movementsl Herein the drivemeans forthecarriage H is suchthat it. may -be driven both ata feed and atraverserate of. movement in either direction; Accord inely, there. isfprdvi'deda reversible electricteed motor EM and a reversible electric' rapid'orltr'av ersei'njotor TM'j'each adapted to be startedland stqpped tostart 'an d stop movement of the cai' riage l I, and to be reversedtoreverse the direction 01.m0veme nt of, the" carriage ,l I. These motorsa connectedjt'o drive thecarriage through a difffeiiential "drivearrangement here illustratedlas a 'planetary'gejar 6.61 19? finerallydesignated at .l 2. This gear devicef comprises a planet gear carrier 113 having teethl 4 formed on the periphery thereof. Meshing with theteleth Misfla gear [5 fixed on one end of'a shaft, s, the otherendofwhic'h carries a gearl 'l of ajlset of pick-off "gears/Theremaining gear I tof this set is fixed on one end of a. shaft I9 ".thefother end'of which carriesa worm wheel 20 which meshes with aworm 2 lfixed on the projecting 'end of the armature shaft 22 or the feed motorThe pick-01f gears 'l"! and I8 ar jm well known manner changeable ,tovary the drive ratio of the feed'moton r f A plurality of stub shafts25am rotatably j ournailed in the planetg'ear carrier [3; these shaftsbeingspaced'oiitwardly equal distances 'frornthe center of'the planetgear carrier l3. Fixed on OJQGIGIld OiBaCIl shaft are thesrespectiveplanet gears Ethanol fixed on the opposite end of each and dwell of theelectrically driven and controlled shaft are he respective planet gears21. The carriage. As to this feature the two control sysplanet -g s 26are in constant mesh with a sun terns about to be described are common,though gear 28 fixed on one end of a shaft 29, the other the particularmanner of obtaining the desired end of 'whi'ch carries a bevel gear 39.Meshed end varies in each system. The systems are also with the yelgearjj is a comilclngi ltary bevel common in many other resgects andtothe degear 3! 0h meander waits? w l ctjcalthef conihrbncoiilsti'lletigns of the a s n other ehdthe i tl lel'ement 331isystem's-Will be described beforeeach system is of a clutch 33. Anotherelement 331) of the treated in detail and alone. Many common feaclutchfixed on the armature shaft 34 of the NY 'tflres of the systems aresimilar to the apparatus rapid ortraverse motor TM}. "fffihe iplanetgear I thapatent to Bertil T. Anderson, No. 21, on the other hand, meshwit a /BQfiiG; 1 April 16, 1946.

fixed on the end of a shaft 36 arr 'I bother theisystems thefeed motorFM and on its other end. This gea'ri firi iotfo are connected inparallel an idler gear 38 on the frame I y arily controlled as tostarting and meshes with a drive gear 39 spli as to direction ofrotation by means shaft 40 mounted to drive the carriagellilg ont tincluding three normounting of the gear 39 p e qn ofrthei mallyvogenswitches FRC connected in the power ar with r p o he, haft b p rmi r lliiiewires and two normally closed switches FRC' tiye movement of the woelements axially of said 20 and FRCS connected in the control portion ofshaft serew haft?o is showgras be the-syst m; andaared ertcontactorinmiidin i a'll a ds i pii enq i is three'florriially-obeh"switches'F fiGi connectedfiri iieiae r tiieca riage;llintermediate the; reverse manner in" thegpower-"line wires and ad Ynormatlyclosed switches FLG and F'LCS n th controlpor tion ofthe system:The swi-tehes -aI-ri'd afreinterposed' in ge i i restart cl- "1rdstoppee etathe nd eirdir gor a? cycle r mov meiit oy wire systemcomprising Theti averse motcr ndepe'ndhtly controlledas toandstQp-fiirig byfinearis of 'a travers'e con ncliidtng 1 three normallyopen switches filr'ictiorfi-to'aintr rliiit' thelcii'ciiit"to thetrayerse motor without disturbing the feed-motor oil-chit foi'ithe-pilrpose o f obtaii'lili'g -a' feed rate or movei rent ol thecar-rla'ge lid to -co'mplete thtctrcilit o ttie raversemoto r-obtainirig a ate ofmovement of sa i c'a'rri'a'ge; {is -traversecon'tactor isinter posed between tiie traverse motor ancl the 1 feedright nd' feed lefficontaetors soz-that direction oi or -tlt'ezt'raversemotor will be underxoon trcl of -the -:fe right and fed' left contactorsthe same as-the feedmotor; biit starting and steeping or tlie traverse imotoris contrond by the ttaverse -contactor anoi-thex-traverse -motor 11 be deenergjized -w-ith'out deenergizing the to d motors l'ft-andirightconta'ctots' f or th'e feedand l actuated electrically'bts-meanfirespectively of a feed right contactor coil FRCC, a feed leitcontactor; cOiIE-FLGQ and a traverse conta'etor coil In addition;- t'o-the' coils just described a'nEaGtuatingfcoil SRGHon akstal ting -re layhaving a single normally open -sWitch -SREL There: is: also; an"actuating coil for: what will herein 'be' t'ermeda holding relay havingzthree switches HRS Ir, and 'I IRS3, :th efirst two normally open andthe third-r-beingmnormally closed. .In: the circuit .of Fig. 21only, twotimer relays'tarelpr raided; the first haying an actuatiin'g'icoil "lRGzand a sing-le n'o'rmallyl closed switch' TRS, and the second havinganactdati-rlg coil Q-Ethe r ed In. 2tI -Rfil asnd a normally open switchZ'IRS'.

the lenergizat, Forming a part common' t botli-systems isa Obtain themlwe unitary controller UC pniividiii'g eombined maii riaanthecantml-sxst l. cal and automatic-actuation and constituting tl-lepr'imary control-means ofthe system. This unitary controller issliowndiagrammatically-in v l l Ffgsifl a lid gf akfid efld elvaitiofiin -Figi 1' and eludes novehmeansistwprotideformpositiveestop "7'5comprises a first coritrfil -measnsl incliidmg a -pm traversemrotorsand' he' -travers'e'contactor are ed upon the shaft "H.

.5 rallity of switches associated "with the feed left and feedrightcontactor coils and with'the traverse contactor coil, therebyconstituting a rate and" direction control; a second control meansincluding a plurality of switches adapted to be manually actuatedandassociated with thestarting relay coil SEC and thereby: constitutinga start and stop control; 'and'a third'cont'rol'means including switchesadapted to be automatically actuated and also associated with thestarting any coil and constituting a 11mm or automatic stop 'control'The unitary controller is claimed and described in detail in theGranberg Patent 2,203,297 dated June 4, 1940! It is believed, how} ever,that the physical construction of the eontroller to the extent requiredfor an understanding of this invention maybe understood from the presentdisclosure wherein the function and operation are clearly set-forth. VThe rate and direction control is both manually and automaticallyoperated, andfmor e over, is operabe independently of the start and stopcontrol and the automatic stop and, limit control, and serves tocondition the controlfcircuit preparatory to initiation of operation ofthe drive means for the carriage. As previously stated, the rate anddirection control comprises a plurality ofswitches associatedwith thefeed {right and feed left contactor coils and the trayerse Contact rcoil. These switches are four in humber as clearly seen in Figs. 2 and3, each additional two pairs of stationary contacts 64, B nd $6, 61 aresimilarly mounted, but on the opposite sideof the controller.

A movable contact 68' adap ed to cooperate with the stationary contacts62,63 and a movable contact 69 adapted to cooperate} with the stationarycontacts t5,'61 are mounted on opposite ends of a T-shaped bracket 1Gpinned to an =oscilla able or rockable shaft; H extending longitudinally of the controller and journalled in the end walls of the casingwhich houses the controller. Simi1arly, a movable contactflZ and amovable contact 13 are mounted on opposite ends of a Teshaped bracket I4which is loosely mount- The contacts .12 and 'lQ areadapted to cooperaterespectively with the stationary contacts 60,-! and 54, 55. Though notshown here, each of the movable contacts its, 69, 12 and 13 in practiceis preferably yield- 2 and 3 and in which bothmovable contacts 68 and 69are disengaged from the stationary contacts, and an extreme position oneither sideof neutral in which one of the switches is closed byengagement of one of the movable contacts with its cooperatingstationary contacts, while the other switch remains open depending intowhich extreme position the bracket ]is swung. The

bracket 14 has but two positions, namely, a right position and a leftposition With thebracket in its left position as shown in Figs. 2 and 3movable contact 13 engages and bridges contacts 64, 65,

while movable contact 12, is disengaged from its cooperating stationarycontacts. When the bracket 14 is swung to its right position just thereverse is true The bracketsia re yieldably retained in their variouspositions by suitable means, such as star' wheel portions each formedwith the requisite number of notches and en gaged by spring pressedfollowers. i

It has been previously stated that the bracket 10 is pinned to the shaftH while the bracket 14 is loose upon the shaft. In order'to obtain therequisite movements of the brackets "land 14 which particularlyadaptsthe controller for use with machine tools and for the systemsherein disclosed, the bracket M is actuated upon rocking the shaft "Hthrough a-lost-motion connection. This lost motion connection is of sucha nature that when the shaft is rocked to swing the bracket in to eitherextreme position the bracket 14 also is 'swun in the same direction, butwhen the bracket 10 is merely returned from either extreme position toits neutral position, no movement is imparted to the bracket 14. Thislost motion connection comprises an actuating lug ,75 disposedcentraily'on the shaft "H with respect to the bracket in and extendingaxially to project between spaced follower lugs it carried by thebracket 14 and extending axially so as to overlap the lug 15.- It willbe seen with the foregoing arrangement that upon rocking the shaft 11 toswing the bracket 10 to its extreme position in a clockwise direction asviewed from the right end in Figs. '2 and 3, contacts 63 and 12 will engage their respective stationary contacts and the shaft H may then berocked in a counter-clockwise direction to swing the bracket 19counterclockwise to its neutral position, thereby disengaging movablecontact 68 while contact 12 remains in bridging engagement with itscontacts 50, 6|. Similarly the bracket 18 may be swung to its extremepositionin the'opposite direction and then returned to neutral in whichevent it will carry with it the bracket 14 when swung to the extremeposition, but will not carry with it the'bracket 14 when returned to itsneutral position, leaving the parts in the position illus' trated.

In order that the shaft H may be rocked both manually and automatically,it projects from both ends of the casing of the controllenand at itsright hand end, as'viewed in Figs. 2 and 3 (this end being herein calledthe forward end) the shaft carries a lever 1'! secured to the shaft H bya pivot pin 18 extending diametricallyof the shaft so that'the lever His held against rotation relative to the shaft but is pivotal in theplane of the shaft. At the opposite or rear end the shaft H hasnonr'ot'atably securred thereto .an arm lfi'carrying a follower 83 foractuation by dogs mounted on the carriage H as will be hereafterdescribed. s s s The manual start and stop control'means' is designed tobe actuated by the lever l! through the pivoting of the lever about theaxis of the pin [8 and thus independently of the rotational movement ofthe lever for rocking th'eshaft H in actuating the rate and directioncontrol. To that end the manual start and stop control coinprises twoswitches formed bythree stationary contacts 85,, 8E and 8?, and movablecontact 88 .in the form of a'tiltable plate provided with contact pointspositioned to cooperatewith said stationary contacts. The particularvconstrue-jtion of this switch means'is fullyfldisclosed in the GranbergPatent No. 2,203,297 above men: tioned. Suffice it to say, therefore,that the movable contact 88 is normallyso heldas tobein engagement.withstationary contactsti and 8 6 but out of lengagement, with contact"8'5, and, through the movement of a plunger 89 whichis agsregoeaactuated; by the lever- 1"! as" diagrammatically shown the-plate88 maybe caused to engage contact 8'! while still engaging contacts 85am-- 86;or to be disengaged from all three contacts. Movement of the p'lunger 89to the left asviewed iii-Figs; 2 .and-Scause's engagementof the-mov'-able contact-BBWith the contact 81 whilemove-= ment of said plunger tothe right results in breaking all of the switches controlled by themovable contact 88.

Atthe opposite end-of the controller is the automatic stop or limitcontrol means. like the manual start and stop control this automaticcontrolcomprises two switches formed by three stationary contacts 98,9-! and 92, and a movable contact 93- in the form of a plate. Here againsuffice-it to say that the movable contact 93 has a-normal position inwhich it is in engagement with all three stationary contacts asillustrated and that said movable contact is adapted'to be actuated by aplunger 9 ltobe disengaged from the stationary contact 9-2 whileremaining in;- engagement with the" contacts 90 and 9|, or to bedisengaged from-all three contacts 98,-!) I-,. 92. The plunger 94carries a'follower 95v for actuation by dogs on'the carriage. Thisconstruction is also more fully disclosed; and claimed in theaforementioned Granberg Patent No. 2,203,297;

While the structure above 'described is similar to the structurefound-in Anderson-Patent No, 2,398,346 above noted, in the systemdisclosed herein the feed brakeelectromagnetcoil 52-and the rapid brake.electromagnet. coil- %5 are connected in a circuit adapted to beenergized from connecting. the stationary contacts 87 andlil is aleadI03 forming .part of a start; or initiating circuit, and another leadlfi l forms part of this same-circuit and is connected at one end to-thestationary contact 9! and at the other end to the line wire L3, the leadI64 incorporating the (1011 SEC of the start relay and series connectedthermal overload safety switches l0! and I02.

This starting-circuit includes the normally closed switch formed by thestationary contacts,

91']; 9| and' the movable contact 93 o'f'the'aut'omatic stop controlmeans, the normally closed switch formed by the stationary contacts 85,86 and the movable contact 83 of the manual start and stop controlmeans, and the normally open switch of that same means formed by thestationary contact 8'2 and the movable contact '88. Thus it will be seenthat if th'el'ever; Tl pivoted to move the plunger 69 to the'left' theswitch 81, 88 will be closed, thereb completing a starting circuit andenergizing the coil' SR'C of the starting relay. This relay, as alreadystated, has a single normally. open switch SR8 which willbe closed uponenergization. of the relay coil. The switch SRS is ina leadlaconimeeting the stationary contacts 86 and 92', the lead I85 togetherwith the switch SRS complet ing a holding circuit for the coil SRO thatmay be traced as follows: line wire Ll; lead 100; closed switch 85, 86,88; lead I05 with the new closed-* s'witch SRS; normally closed switch9|, 92; 93; and lead 'lMto line wire L3. With this arrangementii thelever TI is pivoted to close the switch 81, 88 and energize the coilSRC, closureof the switch SRS forms a holding circuit around the switch87, 88, andthis holding circuit remains closed as long as switches 85;86, 88 and 92-, 93remain-closed.

In addition to controlling this holding circuit for the coil SRCotthestart relay, the switch SRS' also controls all of the othersubcircuits of the control'circuit proper. To that endthere is connectedinthe lead ll5-beyond the switch SRS (that is intermediate'the switchand the 'sta tionary'contacti-JZ) a'lead [c5 which extends'to thestationary contact 64 ofthe unitary con troller; Contact isinterconnected With-com tact -68 of the controller by a lead F31. Theremaining contact-6+ of the pair of contacts'fiil, 61 is by a lead-lil8connected to-theline wire Lfiand has incorporated'therein the coil FRCCof 'thefeed right contactor- FRC' and the mor mally closedswitch-FLCS ofthe feed lef-t contactor.

The coil FLCC ofthe feed left contactor is connected in a sub-circuitgenerally parallel with that of the feedright contactor coilandcomprising alead W9=connected at one end to the stationary contact 65and-atthe other end to the lead 168 adjacent line wire L3. This lead hasincorporated the normally closed switch FEES of the feed right contactorand the coil FLCGofthe feedleft-contactor. Also under the control oftheunitary controller U0 and generally parallel with the sub-circuitsincluding the feed right and feed lef-tcontactor coils isa sub circuitfor the traverse contactor coil-TOG. This circuit isformed by a leadHcconnected at one end to the line wire L3- (through leads I88 and 189)and'at the other endto the stationary contact 63; ;andhavingincorporated therein the coil T00 and the normally closed switch I-IRSB.Stationary contact 62 is by lead I ll connected to the lead H38intermediate the feed right contactor coil FRCC and the feed-leftcontactor switch FLCS to complete a-circuit for the energization of thetraverse contactor coil when the unitary controller is swung to theetreme position wherein the movable contact 68 bridges the stationarycontacts 62, (-53. Stationary contact 53 is also connected to stationarycontact 67 by; alead '2, while contact 66 is by a lead! 13 connected tothe lead I 99 intermediate the reed lef-t. contactor coil FLCC and thefeed right'contactor switch FRCS to complete a cirmm; for energizing thetraverse contactor coil TCC when the unitary controller is swung to the.extreme in' the opposite direction, causing the movable contact 69 tobridge stationary contacts 66, 61.

It is believed apparent from the above that by rockingthe shaft Hthrough the medium of the lever T! the unitary controller is operableto. precondition the control system to bring about movement of thecarriage H in either direction and at either feeder traverse rate at thetime the plunger89 is moved to the left to permit completion of thestarting circuit by closure of the contacts 81, 88. Switch 60, 6!, 7-2conditions the system for operation to the right; switch 64, 6 5, 13conditions the system for operation to the left; and switches 62, 63, 68and 66, El, 68 determine the rate of movement, closure of the selectedone of said switches providing for traverse movement, and opening of 9.said selected switch providing for feed moveinent. Thus if the shaft 'IIis rocked to its extreme position, for example, to the right as viewedfrom the right in Fig. 2 so that both the movable contacts 68 and I2will engage and bridge their respective stationary contacts, circuitswill be conditioned to energize both the feed right contactor coil FRCCand the traverse contactor coil TCC if, while inthat position the leverTI is pivoted to move the plunger 89 to circuitior'th'e traversecontactor coil TCQ iiicludeslthe switch 62, 83, 68, and hence in suchevent only the feed right contactor FRQ would havecl'osed, with theresult that the' 'c arriage Wouldhave" been driven at a feed rate totherightT'as viewed Fig. 1. Conversely, if the unitary controller is swungto its" extreme "in the opposite direction (counterclockwise asviewedfrom" the right in Fig.'2 ),rnovable contacts 69 and I3 willbridge contacts 66, 61 and 64,155, respectively, and will conditioncircuits for thetraverse'contactor c'oil TCC and for the feed'leftcontactor coil FLCC." These last mentioned circuits may be traced asfollows: line wire L3; lead I 08{ lead .|f09*inc1uding feed leftcontactor -Ycoil FBCC and switch FRCC; switch 64; '65.;1332' lead I06;lead I05; switchfillj'fi, 93"; lead-7W3? switch 85,81, 88; and lead IOU'to line wire-.LI. ;.If switch 92,v 93-or switch 81, '88 is open, and ifcoil SEC has been previouslyenerized: th'e holding circuit" throughthat'portio'n oftthe lead whichiincorporates the switch S RSshorts-around the above? mentioned "open circuits? The circuit for coil-TCC'isas follows: line wire 113; lead; III] including ftraversecontactor coil T; and switch mass; lead' n2; switch 66,151;

69;" lead I13; lead I09 (including switch'FRCSH switch; 384, "65,113;lead I'lifiy'lead I; switch 98, 92,- 93;ylead I03; switch85, 81, 88';and lead IIIDtoline wireLIr It" will be seen that with the'parts in:this'posi-' tion and the switch 8I, 88 cl'osedthes coils will beenergized and the. feed leit contactor switches and the traverse"contactor switches TC closed to drivethe carriage at a traverse rate;

but this time to'theleft as viewed in Fig; l'because thedirection ofrotation of the motors has been*reversed"due tothe supply of power thereto; through the feed left contactor rather than the feed rightcontactor. the carriage to "the left at' 'a feed rate might be initiated-if the unitary controller were returned toneutral positionrtobreak thecircuit for the traverse contactor coil at the switch- 66; 67, 69*

while preserving the circuit for the feed left contactor -coilthrough"switch 64,?65', I3: It "will be understood; ofcourse,-that operationofathe rnoto'r may .be-arrested at; any time bymanualsfl'iiftJoffthe-plunger 89 to the right as viewed in Figs.. 2 and.3. thereby breaking the holding cathe er thestar ting relay at theswitch 85,

8'6 '88. Similarly, the ,Operationmay be arrested antonratically by.. shift oi the; plunger- 84 to the Again movement" of right, breaking theholding circuit at the switch 9|, 92, 93. The plunger 94, as previouslymentioned and as will hereinafter be more fully described is adapted tobe actuated by dogs on the carriage I I.

' The circuit illustrated provides an arrangement whereby, while thecarriage continues to be driven at a feed rate in one direction, theunitary-controllermay be actuated to precondition the system fortraverse movement of the carriage in the opposite direction. To thatend, holding circuits are provided for the feed right and feed leftcontactor coils. These holding circuits are under the control of theholding relay HRC, and more particularly under the control of its twonormally open switches I-IRSI and HRSZ. The holding circuit for the feedright contactor coil comprises simply a single lead II 5 connected atone end to the lead I85 intermediate stationary contact 92 and switchSRSjand connected at the other end to the lead I 08 intermediate thestationary contact 6|, and the eed leftjcontactor switch FLCS and havingincorporated therein the holding relay switch HRS I. The holding circuitfor the feed left contactor coil comprises a single lead 6 havingincorporated therein the switch IIRSIand beingconnectedat one end to thelead I I5 intermediate the lea'd I05 and the switch HRSI, and at theother 'end to the lead I09 intermediate the con tact 65 and thefeed'right contactor switch FRCS.

The energizing circuit for the coil HRC of the holding relay comprisesalead II'I connected at one end to the lead I intermediate stationarycontact 52 and switch SRS, and at the other enidlto the line wire L3through a portion ofleads I-ID, jil9andll'fl8. This lead hasincorporated therein a idog-actuated normally open limit switch LS and anormally closed timer relay s'witchTRS; f

As'previously stated, the primary object of this inventionis to provideimproved means for 0htaining llOSit iYe sto'pjand dwell in anelectrically driven and electrically controlled system. This object isattained through the provision oif a variable torque brake for thetraverse motor whereby, in Fig. 2, full torque is applied at thebeginning of the feed operation and after a short time delaythetorque isreduced. At this point in the feed operation the torque is'high enoughto allow'the feed movement of the table but low enough so that when thetable hits the positive step the brake for the traverse motor begins toslip so-that the carriage is held against the posi? tive stop bycontinued operation of the feed rjnotor, but injuryto the mechanism isprevented by permitting the feed 'motor' to drive the traver'se motorduring t-h'e'period of the dwell." In order to attain this object themagnetic brake fohthe traversemotor is provided together'with novelmeans for operating the brake apparatus; Referringagain to Fig. 2 therectifier 98 has its inputterminals connected across the power' line, 'alead I28 connecting one side 'oi said rectifier tothe' line' wire L'I"through a "portion of the'lead I110, and a lead I2I connecting the otherside of said rectifier to' th'e'line wire L3 through a portion of "the"lead I081 first outputternii nal'of the rectifier is connected by meansof a- 1e'ad'122 directlyto one side" of the feed brake; electromagnetcoil 52 and the rapid'brake electroinagnet coil 45 in parallel, and theother out-' put-iterminarof the'rectifijer is connected to" said coilsthrough a parallel circuit. The portion'of this I circuit which connectsI to the 1 feed brake electromagnet coil- 5.2 comprises-a lead l-2.3rwhich incorporatesinseries thefourth normally closed switch FROassociatedwith. the feed right con-- tacton; the fourth normally. closedswitch FLC associated with the feed left contact'orrand a variabletorque adjustment resistor 124. The portion of, this circuitwhich-connects tothe traverse brake electromagnet coil 45 comprises alead- I25 connected to said first output terminal through the lead 123'-and incorporating in series the fourth normally closed switch TCassociated with the-traverse contactor, and a--torqueadjustment resistor125:. A subsidiary parallel circuit for shunting around this lastmentionedresistor includesa lead 521 which isconnected-to the lead Il-SL011; either side of the resistor I26 and which has; incorporatedtherein the normally open s x/itch ZFERS of the; second timer.

'It will be obvious that when the feed right contact'orcoil FRCC. andthe feed left contactor coil ELCC are both deenergized-the switches EEGand ELC' will be closed and the feed brake electromagnet coil 52 will beenergized, applying braking torquc to the feed motor in: an amountdepending upon'the adjustment of the resistor !24. llhis;adjustment isreadily-made by moving the slider l-Zia, and the higher the resistancein the circuit the-lower the braking torque will be. Similarly. wheneverthe traverse contactor coil. TCC isldeenergized the switch TC willlbeclosed and the;. rapid. brake electro-magnet coil 45- will be energized,and the degree of energization and consequently the amount of torqueapplied-by the brakesassembly dto the traverse motor will depe dfuponthe adjustment of the slider [26a on the variable resistor I 2%..However, it will be noted that; in this circuit that whenever the switchZTRS is closed the lead.- IZT shuntsaroundthe. resistor. E26 andeffectively removes it. from the circuit so that the full voltage outputofthe. rectifier is applied across the coil 45,. Theenergizing; circuitfor the coil TRC comprises a lead I=28eincorporating said coil thereinand-connected one end to the, lead H1. intermediate the syitchesLS andTRS and connected'at the other end to the line wire L3 through the leadsHll,

HBQs-and" 1B8. Theenergizing circuit for the coil ZT RC comprises a leadI29 incorporating said:

colt-therein and connected at one end to line here through leads 12a,m1, lll9and its, and: connected at the other end to lead H inter mediatecoil 'rcc andgswitch HRS3.

Having'describecl the elements of the systemit isgbelievedthat theinvention-can befurther clarified; and rendered more readilyunderstandable; him-a: brief description of the'operation of thisfornrof the invention; course,- that a great number of different cycles;of operation, are attainable with thersystem herein disclosed: Thesecycles may be arranged to-obtrain the so-called skip-feed milling, or:the sooalled -double end milling and itis tobe understood that theinvention is not to be limited to theone; cycle hereafter employed byway of ex-' emplary disclosure. For example, let it beass-umed thatthe'carriage II is to have a cycle composed of a traverse movement tothe right, followed by a feed movement to the right, a dwell,,and then areversal and a. traverse movement;tothe left back to itsinitial startingposition; Under these conditionsthe left'endof-thecarriage as seen inFig; 1 will'haveadjustably' mounted thereon a positive stop screw" I30;Po-

sitioned to be abutted-bythe' screw to. hold the; carriage: againstfurther. movement" to thearight It is to he -understood,- of

isa steel plug; it. having;arreduced portion I32 inserted into avrecessfor-med; in the base Ill; of the machine. Four dogs-DI, D2,D3'and- D4-are mounted on the carriage H and: aresuitably spacedlongitudinally of the carriage. The dogs DI and D2 are designed to, actupon thefollower 8Elcarried on the shaft l I of the-unitary control: lerUC. The dogDJ" functions to rock the con-w troller from itsfeed rightposition whereintboth the switches 62, 63,. 68,; and 65', 67, 59 areopen; but the switch 66, 61,12 is; closed, to its traverse left,position I wherein; the; switches -65, 6-1, 69: and 64, 65, 13 areclosed; "I'he;dog D2. funct-ionsto. rock theunitary cont-rollerfronritstraverse; right position toits feed right. position-whereinbothswitches associated withithe arm-lll are open'but the switch 68,- 6-|,12- is closed. The dogD3 is adapted toengage the-followersd on-theplunger' 94- and cause opening of the: switch. 9I-,l92, 9.3: which.Will' arrest'operation of'the motors; and bring thecarriage to a. stop;These-dogs; in terms of their functions may beknown respectively as thetraverse: left dog, the feedaright dog; andthe stop dog. The dog D4 actsto controlithelimit switch LS andis sQ-positioned-- aslto close thisswitch; just a; brief interval prior toengagee ment of thestop screw I38withlthe plug; Isl-and also prior-to engagement of the dogxDl withthefollower of the unitary controller,1and:tomain tain the limit switchclosed. during the dwell period and until traverse movement to; the:left has been initiated.

Letit be assumed; therefore; that the. carriage H is in its-normalor:stopapositionishown ill-Fig; land that the dogs Dl-, DZ, Da'andDdhave been; set up toproduce the cycle: above described; Toinitiatemovement ofthecarriage Iii to the right at a rapid or traverserate the operator grasps the lever'l'l and swings the samertoiits'extremerightposition (clockwise looking: from: the right in Fig. 2)tocondition.energizing. circuits for'tl'ie feed'right contactor coil.FRGC. and the traversecontactor coil TCC by closure ofitheiswitchesfillg 6|; [2 and 62, 63," 5.8, respectively. The circuits may be'tracedas-gfollows: lead wil closed switch 8%;88, lead lflsmontaining. the.normally and hence now open switchSRS 'ofth'e starting relay, lead IGG;lead I01, switch 61);:61, 12*,andl'ead Hl8' containing the now: closed 1switch-- FL-CS of the" feed left contactor'and coil FRCC of. thef'eed'right oontactor; leads: I00: and? IE8? being con nected respectively toline wires L'l and The circuit for the traverse contactor coilTCCis-common with thecircuit for the. feedsrightcontactor: coil tothepoint: beyondnthe;feeclz'leftcontactor switchFLGSwherelead l-.l.-'l'=branches offto the stationary contact, 62. The" circuit. forthe-traverse; contactor coil is completed through: the switch 62, 63, 68and. the. lead: Iii! which incorporates the normallyclosedis-witch.HRS3' and the traverse, contactor coil TGCb-eyond which saidlead is connected to. the: line wire 153':

Because of the presence: of the open switch- SRS in the commoniportion'.of these conditionedcircuits, the feed right.- andtraverse. contactorsare,,of course; not caused toclose and henceno= operation of the motors:and no movement of thecarriage takesaplace. While still holding'the;lever l7 swung'to its extreme clockwise position as above describedtheoperator pulls the top: of' the lever toward him to forcethe plunger8'9Ito. the left in Fig. 2 and closethe starting; switch by engagementofthe contact 8'! by'the movable;

contact 88. This complet'esthe energizingoincuit for the starting relaycoil'SRC which-circuit anemia may be traced as follows: line wire LI,lead I; switch'85, 81, 88, lead I03, the closed switch 90, 9|, 93, andlead I94 through the coil SEC and the safety switches IUI and I02 toline wire L3. It is to be noted that this starting circuit may becompleted even thoughthe-dog D3, still holds the plunger 94 depressed tobreak the holding circuit forthe starting relaycoil at the contact 92,for the starting circuit remains closed through the switch 90, BL. 93.Energization of the relay coil SBC closes the switch SRS whichcompletes'the preconditioned circuits to thelfeed right contac tor coilFRCC and the traverse contactor coil TCC thereby initiating operation ofboth the feed and the traverse motors in such direction as to causemovement of the carriage at a traverse rate to the right. At the sametime'it will be noted that the switches FRO and TC are opened upon theenergization of the respective coils FRCC and T00, releasing the brakeon both the feed and traverse motors and that coil 'ZTRC is energized;its circuit being common with thatof the coil TCC'to a pointintermediate closed switch HRS 3 and vcoil ICC and then branching offthrough lead I29, coil ZTRC, lead I28, and leads I10, I09 and I08 toline wire L3. Energization. of coil-@2TRC- closes switch 2TRS and"closes. shunt lead I21 around resistor 126. With the first movement ofthe carriage to the right, the dog D3 releases the plunger 94 and themovable element 93 of theautomatic control means engages thestationarycontact 92 to complete the holding circuit for the start relay coilsothat the operator may release the lever I1. l r

i T he carriage will continue its movement to the right at-a traverserate until-the dog D2 engages the follov-zerv 80 and rocks the shaft IIof the unitaryscontroller to its-feed right position wherein theswitch62, 63, 68 is opened, but the switch 69, GI; -12 remains closed.This ,action breaks the circuit to. the traverse contactor coil TCC andthe tiifr'ier con zrac becausethe switch 52, B3, 68 be;

tween the leads I Ifiand II I. isopen, but because of the lost motionconnection between the lug15. fixed on the shaft TI and the lugs IS onthe bracket T4 this return of. the shaft to its neutral posi-v tion doesnot affect thebracket T4 and hence the carriage will move to the rightat a feed rate. v When the feed portion of the cycle is initiated asabove described by opening the switch 62, 63, 68 the coil .ZTRC isdeenergized as noted but the switch ZTRS remains closedduring the delayperiod of the timer mechanism sothe shunt circuit through the lead 21 isnot broken until after this delay. period. When the. coil 'ZTRC isdeenergized, the core thereof returns to its position as shown in Fig.2, thereby allowing the switch ZTRS toopen; said switch isretainedclosed-by the time ing device shown diagrammatically as T.-D.until the, passing of a predetermined time. Further.-

rnore,.it will ben oted that. deenergization of the 7 traverse contactor0011- T00 results in closureof the switch TC, thereby completing acircuit to energize the rapid brake electromagnet. coil 45, this circuitextending, from the rectifier .98 through lead. I23, lead I25,switch'TC, shunt lead I27, switch ETRS, lead I25, electromagnet brakecoil 45, and, lead I22 back to the rectifier. Inasmuch as the switch2'IRS was closed there Was a short circuit throughthe lead IZ'Iaroundtheresistor I26 and the coil 45"wasenergized 1-4 speed-to the desiredfeed speed. Shortly thereafter upon the operation of the mechanicaltimer mechanism theswitch 2TRS will open, breaking the lead I21 andremoving the short around the resistor I26 and placing said resistor inseries in the circuit with the coil 45. The torque is now reduced to avalue which is still high enough to insure movement of the table but lowenough to insure that when the table is positively stopped the feedmotor. will drive the traverse motor, the brake slipping for thispurpose. Adjustment of the slider IZIia may be made at any time toincrease or decrease this torque. a While the carriage is moving to therig-ht at a feed rate, and ate. suitable time prior to engage mer tofthe dog DI with the follower 80, the dog D51 closes the timer dwell orlimit switch LS Closure of the limit switch will energize the coil HRCof the holding relay and this relay will in turn establish a holdingcircuit for the feed right contactor coil FRCC independent of theunitary controller, and thus permit conditioning of the unitarycontroller for reversal of the carriage and movement to the left at atraverse rate, though the carriage continues inits movement to the rightuntil the stop screw I30 engages the member 5 3 Ito provide a positivestop. The circuit for the holding relay coil HRC may be traced asfollows; lad Hi6; closed switch 85, 86, 88; lead I65 containing the nowclosed switch SRS; lead I I1 containing the now closed limit switch LS,the normally closed timer relay switch TRS and coil I-IRC; and leadsIIH, I09 and I08 to line wire L3. The holding circuit for the feed rightcontactor coil may be traced as follows after energization of theholding relay: lead I60 to I05 as just the lead I56 which incorporatesthe last named switch. Thoughthe switch HRS2 is now closed, energizationof the feed left contactor coil FLCC cannot take place because theswitch FRCSof the feed right contactor coil is still open. Also as aresult of the operation just described the third switch HESS on theholding relay is opened, and.

it is impossible to energize the traverse contactor coil TCC or thesecond timer relay coil ZTRC so long as this condition is maintained.Furthermore, the ,coil-TRC of the first timer was ener-.

gized upon closure of the limit switch LS since this coil is connectedbetween line wire L3 and lead II! by leads H18, I09, I I6 and I28, andthe timer ZTD, which is similar to the device TD,

starts to run. However, the switch TRS does not open immediately uponenerg-ization of coil TRC, but its opening is controlled by the timermech amsm.

Following closure of the limit switch LS and while switch TRS remainsclosed, the dog DI comes into play and rocks the shaft ll of the unitarycontroller to its extreme left position as viewed in Fig. 1. As a resultthe unitary controller conditions circuits for the feed left COIL-wtactor coil and the traverse contactor coil. These circuits maybe tracedas follows: lead I09; manual stop switch 85, 86, 88; lead I05 containingthe now closed switch SRS; lead I05; the now closed switch formed by thecontacts 64, 65, I3; and lead I09 containing-feed left contactor coil'FLCC and memoir Gaining the -still open "reed right-hontacto'rThe'circuit-forthetraverse con tactorc'oili-scornzhonto "a'point beyondthe switch where it branches-off -f-roin' the' lea-d I69 Whilesti-lloldtainingnipi ement f-'the-carria'ge"to v the right at a feed rate is-rnade possibleby provision of the holding circuit for the feed rightce'ntac'tor coil; such circuit being governed as above described by theholding relay 'I-IRC which ettirh launder-"the control of thelimit-switch ES and the delayed action Switch TRS .Of the timer-wens.-

f Asme'ntione'd earl er, when-the "positive stop screw 1-30- engages thesto'p'rnember I SMnoveiheht of "-the--table-s'tops, the ieedmotorcontinuing to and the feed -rnotor rotating the-traverse motor-becauseof the reduced torque on the brake c-aus'edby "the removal "of the shuntcircuit 121'. Gonseaue'ntlythetabledwells-in this positionuntilthe-first tirner drops out andswitch' TRS'open's.

A'fter the-desired dwell, determined bythejset ting-of the firsttinier'relay; the timerirelay switch TR'S opens, breaking thecircuit tothe coil HRC of fthe holding relay and thereby openihgthe stvitch 'HRSiin the holding circuit for the feed right'eontactor coil, andwithdeen'ergiza-tion' of this' coil the feed right contactor will'beoperated; opening thethreeswitch'e's FRC and clo'singith'e switchesPRC. Similarly, :clojsing Zo'f the" holding relay switch HRSB conditionsthe apparatus -f'or the "energ'ization' or- .the traverse co'nta'ctorcoil TCC and the second timer relay coil ZTRC. In addition, circuitshacl previously. been'c'onditioned as-abovedescribed'for energize tionof the feed l'e'ft contactor coil and the traversemontactor coil.\Vithreturnoffthefeed right c entactor FRC to its normal position(including closureof-the switch FRCS') and-with the:c1osure of theswitch HR'SE these preconditioned-circuits will be 'eoinplete d to-thefeedlert' and to 'thetraverse contaetorcoil's. Ther'eupon,"both the feedleft contactor and-the-traverse contactorcoils "will be energized and*these 'contactors will be operated; closing the switches FLU andopening the switches FLG' and' FTL 'CS associated'with-the feedleft'-contactor and closing the "switches TC ian'd opening the-switch TCassociated withtthe travers' contactor. V

Wh'en the-switch TC opens as-above'describeii the-circuittothe rapidbrake electromagnet'coil Mivillib'eoiaene'd and the brake will becompletely released. As -'the carriage -rnoves to the left at atraverse'rate the dog D4 will no longer exercise control over the limitswitch LS which will then return to its normal open position and-thefirst tiinerrelay will restore its switch'TR'S'toitshormally 'closedposition. When'the carriagereaches its normal or starting position,- thedog D3 will ae'tuate'the p1unger-9 4' to break the holding circuitforthe'cofl SRC of the starting reiayjvvhichwtill in 'turn cause theswitch SRS to open, breaking coils andthe carriage will come to rest inits-final position-with theswitches in the position shown 1 6 is=-c1osedand"'the feed"brake electromagnet coil 52 as'aiso energrzed sincethetswitches FRO 1 and F156" are'closedithus insuring full-brakingtorque td-stepfooth inotors.

acme rbm that diselosedinFig. 2-in theeliinination of one'bf 'the timerrelays and'in providing anarrangement-wherebythe' torque'on the brake isnot reduced until the dogDd'contactsthedwell 1 time 01 "limit switchiisn'ear the endofthe-f'eed d po'rtien of 'he'=cycle is of no import s'o mnes the tcrque is reduced to i a point Where it fa low enough t'opermit-the bra-keto slip to 'relieve are l os'itivel i stoppedi ime(seen switch QTRS h'avebeen omitted n'g tir'ner-compr-ises'a'coilTRCsiin oilTRc of Fig '2-and-connec'ted into exactlythe same manner, the "lead EEG-connecting one 'endof 'said coilwith thelead H 'Fa d 06 ctiiig the'other endof said coil'With "fthi o u'gh-portions:of 'theleaiis 'l m; d B8 50*thaitthecoil TRiC" isen'rfi'z'dwhen the dg g -Dfi dis'es the Ii1nit or dwell timer switch fis and is-dee'nergized when this; svvitchis' opened in the same manner'as-thecoil TRIO of 3' Fig 2. The "timer includes a normally closed SW1h-TBIS wliichis *similarin; operation to the sWith TRjS OfFig; '2 andwhich does not open immgg teiyupon energization of the associated coilTRC', jblltr "which opens after a time delay determined by the setting"of the timer. "This switch"istincorp'orated inthe lead I H and formspart"of=ftheenergizing circuit for the coil HRIC, the amount of timedelay determining the dwell perio'd of-fthefmachine. ,Theil'ea'd P21which form's-a shunt or shorting ciijcuit-aroii'nd the :torque.adjustment resistor l 26' includes 'a' normally "closedfswitch ZTRS'Which'is similariniunction tothe switch ZTRSofthe-secdhbltirn'e'rgioffFignl .Th'e s'WitchiTRSf does not hail'le'ftime'dlayedactiongbut'is' operated by a di-' rect 'rnechanical connection tothe armature of the timerjrelays'othat when the relay is .deenergizefd'the switch is in its normal closed position, and the-switchisopened whenever the coil TREI' is energized. "Consequently, under normalconditions the'- lead I 2'1;forms a short around theresist'or'l'fifi'andif'the rapid brake electromagnet" v V v I "in Itheoperation of the system of Fig. .3 the the circuits tothe feedleft andtraverse contacto'r' ohrationiis iex'actlytheqsame as that describedinconnection with 1Fig.12.down to the point where thejfeedjportionofthe.cyclelis initiated. When tIie 'd-QQD ZQengageS the {follower 8'0.andlrocks the shaft H of 'the unitary controller to its feed rightor'm'o'f the invention disclosed in Fig.

11 position, the traverse contactor coil TCC is deenergized in themanner described in connection with the operation of the apparatus ofFig. 2, and the switch TC closes, completingthe circuit to energize therapidbra'ke electromagnet coil 45. Since the timer relay coil PRO 'isnot energized '(thelimit switch LS being open) the lead I21 is closedand formsarshort around the resistor! and full braking torque is appliedto stop the traverse motor and insure that the table immediately slowsdown to itsdesired feed rate of travel. The apparatus remains in thiscondition until the dog D4 closes the limit switch LS, energizing thetimer relay, coil TRC and the holding relay coil HRC. When this actionoccurs the switch ZTRS' opens immediately, breaking the lead 121 and thetorque of the brake is reduced since'partof the voltage output of therectifier 98 is now developed across the resistor I26. The switch TRS,however, remains 'c'los'ed during the period for which the timer is setto provide the dwell period of the machine, and the table continues tomove to the right until the positive stop screw I30 engages the stopmember l3l When the timer operates to open the'switchTRS' and terminatethe dwell period the motors TM and'FM are caused to reverse in themanner described in connection'with Fig; 2 and thetable moves to theleft atatraverse rate. As earlier described this movement frees thelimit switch LS and this switch returns to its normal open position,breaking the circuit to the timer relay coil TRC' so that the switch Vthe motors and the carriage to drive the carriage at a feed ratewhen onythe first motor is operating and at a traverse rate when the secondmotor is operating, friction brake means for said first motor includinga first electromagnet coil and a first variable resistance in seriestherewith, friction brake'meansior' said second motor for holding saidsecond motor against rotation while the"carriage is being driven at afeedrate, said brake including a second electromagnet coil, asecondvariable resistance in series therewith and a shunt circuitconnected across saidrsecond resistance, an electric controlsystemcomprising means for deenergizing both coils to control operationof the motors to obtain movemrnt of the carriage in one directionat atraverse rate, means operable at a predetermined point in said move:ment to deenergize said second motor and en 'ergize said second -coilthrough said shunt circiiit to apply saidb-rake to said second 'motor tostop rotationoi said motor and cause; said carriage to move at a feedrate, a timer relay having a first normally closed switch connected insaid shunt circuit and a second normally closed switch arranged to openafter a time delay when said relay is energized-means operable as thecarriage approaches the limit of its movement in the one direction toenergizesaid relay to precondition thesystem for movement of thecarriage in the opposite direction after saidtime delay whilemaintaining movement in vthe first direction until the carriage engagessaid stop, energization' of said relay opening said first switch tobreaksaid shunt'circuit for reducing the brakin torque on said second motorto cause the brake to slip and permit said first motor to drive thesecond motor when said carriage engages the stop, the reduced torquebein highenough to prevent the first'motor from driving the secondmotorbefore the carriage engages the stop, variationbfsaid'firstresistance determining the braking torque onsaid first motor when thefirst coil is energized, and variation oflsaid secondresistancedeterminingthe braking torque on said second motor when said second coilis energized and said firstswitch is open.

2. In a machine 'havin a reciprocable carriage, a positive mechanicalstop for limiting movement of the carriage in one direction and meansfordriving the carriage at feed and traverse rates including a firstreversible electric mo tor, a second reversible electric motor, aplanetary gear system operatively interposed betweenthe motors and thecarriage to drive the carriage at a feed rate when only the first motoris operating and at a traverse rate when the second motor is operating,friction brake means ior said sec ond motor including an electromagnetcoil, an electric control system comprising means con trolling operationof the motors to obtain moves ment of the carriage in one direction at atrav erse rate, means operable at a predetermined point in said movementto deenergize said second motor and energize said coil to apply thebrake to stop rotation of said second motor and cause said carriage tomove at a feed rate, a timer relay having a first normally'closed switchconnected to said coil and a second normally closed switch arranged toopen after a time delay when said relay is energized, means operable asthe carriage approaches the limit of its movement in the. one directionto energize said relay to precondition the system for movement of thecarriage in the opposite direction after said time delay whilemaintaining 'movement in the first direction until the carriage engagessaid stop, energization of said relay opening said first switch toreduce thebraking torque without releasing the brake to cause the braketo slip and permit said first motor to drive the second motor when saidcarriage engages the stop, the reduced torque being high enough toprevent the first motor from driving the second motor before the car:riage engages the stop, and means for readily adjusting the brakingtorque when said coil is energized and said first switchis open. V

3. In a machine having a movable carriage, a positive mechanical'stopfor limiting movement of the carriage in one direction and means fordriving the carriage at feed and traverse rates including a firstelectric motor, a second electric motor, differential drive meansoperatively interposed between the motors and the carriage to drive thecarriage at a' feed'rate when only the first motor is operating and at atraverse rate when the second motor is operating, friction brake meansfor-said second motor for holding said second motor against rotationwhile said carriage is being driven at a feed rate, an electric controlsystem comprising means controlling operation of the motors to obtainmovement of the carriage in one direction at a traverse rate, meansoperable at a predetermined point in said movement to deenergize saidsecond motor and apply said brake to cause said carriage to move at afeed rate, a timer relay having a first switch seismic associated withsaid :brakeand a second switch which is .normallyrciosed-and is arrangedto open cperating said first switch to reduce the braking torque withoutreleasing the brake to cause the brake .toslip and permit said firstmotor to drive the-second motor when said carriage engages the stop, thereduced torque being high enough to prevent .the first motorfrom drivingthe second inctorlbefore the carriage engages the stop.

In a )machine having .a reciprocable carriage, a positive mechanicalstop .for limiting movement of the carriage in .one direction and meansfordriving the carriageatieed and traverse rates including a firstreversible electric .motor, .a second reversible electric motor, aplanetary gear system operatively interposed .between the motorsandthecarriage to drive the carriageat-a feed rate when onlythe first motoris operating and at a traverse :rate when the second ,motor isoperating, .iriction brake means foresaid :first motor including a firstelectromagnetcoihanda first variableresistance in series therewith,rfriction brake means .-for said second motor including-a secondelectromagnet coil and :second variable resistance in series therewith,torque-control means 101 said second .Jorake including atimerrelayhaving .a switch associated therewith and connected in :a circuit in:shunt with said second variable resistance, .said switch being closedwhen said .relay 1 is energized and 1-being arrangedto openaftern-Itimedelay when said relay is rdeenergized, an electric controlsystem switch [opening fatter esaid time delay to break said shuntcircuit :for reducing the braking torqueronsaidiseeond motoreto09318613116 brake to slip-,and permit said .Jfirst motor to drive thesecond nl0t0i when :said carriage engages the stop, the treduced torque:being high enough to prevent the first motor ir-om :driving the secondmotor before the marriage engages the "stop, means operable (as "thecarriage approaches -.the limit efits'movementin the one-direction topreconditionth-e: controlling meansufor reverse movement of the carriagewhile maintaining movement in the first directionpand asecond "timerrelay for --initiating drive of the carnage in :the opposite direction*nnder theecontrol roof said preconditioned :means, varia-tion 'of :saidfirst iresistance determining the "braking torque :on said first motorwhenthefirst coiliis energized, and variation vof .said secon'dresistance determining the braking torque son said :seoond motor "whensaid :second :coil fis renergized and said switch is open.

' 1 In :a :machine .ziiaving a :reciproca'ble carriage, a positivemechanical stop for limiting movement act the 'fcarriage :in :oneidirection and for :driving the carriage :at f eed a'nd travverse :ratesincluding :a first reversible electric motor, ;a second reversibleelectric motor, :a planetary gear :system'bperatively interposed .be-=tween-the :motors and the carriage to drive the carriagezatafeed'rratewhen only-the first motor is :operatingand =at;a*tra-verse rate when-thesec- :ondmotor is operating, friction-brake means .for said second motorincluding an electromagnet 011.,"IOIQHE controlimeans for saidbrake'including 'a timer relay having :a switch associated therewith,said switch being closed when .said relay ;is energized and "beingarranged to open aftervaxtime-delay whensaidrelayis deenergized, anelectric :control system comprising means for energizing said :relay and{for 1 controlling operation pf the motors to obtain :movement of thecarriagei-nonedirection at-.a traverse rate, means operable at apredetermined point :in said :movement to deenergize said relay and saidsecond motor and energize said coil to apply said brake to cause saidcarriage to move at a feed rate, meansessociated with-said1brakefor-reducing the braking -.to.rque "without deenerg-izing said coil uponthe opening ofa-saidfswitch afterzsaid time delay topause the brake toslip and permit said first ..-motcr :to drive the second motor when saidcarriage-'rengages the stop, thereduced torque beingxhigh enough to;-prevent the .first motor from drivingethe second rmotor before thecarriage engages the stop, --means operable as the carriage approachesthe limit ofzits movementzin the one direction 'to precondition thecontrolling means ionreverseimovement of thecarriage-whi'le maintainingmovement :in the first direction, and a second timer relay forinitiating drive of the carriage in the opposite directionunder-thecontrol of. saidipreconditioned-means.

*6. In a ,machine havingia movable carriage, a positive rmechanical stopfor limiting movement 0f the carriage in one direction and means fordriving the carriage at feed and traverse rates 'includingafirstelectric motor, :a second electric motor, difieren'tial drive meansoperativelyinterposed between the motors and the carriage to drive thecarriage ata feed rate when only the first motor is operating and at.atraverse rate when the second motor is operating, friction brake meansfor said second motor for holding said second motor against rotationwhen the carriage is being driven at a feed rate, torque control means'for said brake including a timer relay having aswitch associatedtherewith, said switch being closed'when said relay is energized andbeingarranged to open after a time delay when said relay-is deenergized,an electric control system comprising meansyfor energizing said relayand for controlling operation of the motors to obtain movement of thecarriage in oneidirection at a'traverse rate, means operable at apredetermined point'in said movement to deenergize said relay andsaidsecond motor and apply said brake to cause said carriage to move at a.feed rate, means associated with said brake for reducing thebrakingtorque without releasing the brake upon the opening of saidswitch after said time delay to-o'ause the brake to slip and permit saidfirst motor to drivethe second motor when said carriage engages thestop, the reduced torque being high enough to prevent the first motorfrom driving the second motor before the carr-iage engages the stop.

7. In a machine having a reciprocable carriage, a positive mechanicalstop for limiting movement of 'the carriage "in one direction and meansfor driving the carriage at feed and traverse rates i 21' eluding afirst reversible electric motor, a second reversible electric motor, aplanetary gearsystem operatively interposed betweenthe motors and thecarriage to drive the carriage atxa feed rate when only the first motoris operating and at a traverse rate when the second motor is operating,friction brake means for said first motor including a first,electromagnet coil and afirst variable resistance in series therewith,friction brake means for said second ,motorincluding a secondelectromagnet coil, a second variable resistance in series therewith anda shunt circuit including'a switch connected across said secondresistance, an electric control system comprising means for deenergizingboth coils to control op.- eration of the motors to obtain movement ofthe carriage in one direction at a traverse rate, means operable at apredetermined point in said movement to deenergize said second motor andenergize said second coil through said shunt circuit to apply said brake.to said second motor to cause said carriage to move ,at a feed rate,means for opening said switch to break said shunt circuit. for. reducingthe braking torquejon said second motor to cause the brake to slipandper mit said first motor to drive the second motor when said carriageengages thestop, the reduced torque being high enough to ,preventthefirst motor'from driving the second motor before the carriage engagesthe stop, means operable as the carriage approaches the limit of itsmovement in the one direction to precondition the controlling meansforreverse movement of the carriage while maintaining movement "in thefirst direction, and timing means, initiating drive of the carriageinthe opposite direction under the control of said preconditionedmeans,variation of said first resistance determining the braking torque onsaidfirst motor when the first coil is energized, and variation of saidsecond resistance determining the braking 'torqueon said second motorwhen saidsecond coil is energized and said switch is open. i r.

8.. In a machine having a reciprocable carriage,ja; positive mechanicalstop for limiting movement of the carriage in one direction and meansfor driving the carriage at feed and traverse 1 ,rates including ,a,first reversible e ectric motor, a second reversible electric ;motor, aplanetary gear system operativelyinterposed between the' motors and thecarriage to drive the .carri'age'at a feed rate when only the firstmotor tion of the motors to obtain movement of the carriage in onedirection at a traverse rate, means operable at a predetermined point insaid movement to deenergize said second motor and energize said secondcoil to apply said brake to said second motor to stop said second motorfrom rotating and cause said carriage to move at a feed rate, meansoperable during such feed movement for reducing the braking torque onsaid second 'motor without deenergizing said second coil to ing thesecond motor before the carriage engages the stop, means operable as thecarriage approaches the limit of its movement inthe one direction toprecondition the controlling means for reverse movement of the carriagewhile'maintaining movement in the first direction, and timing meansinitiating drive of the carriage in the opposite direction under! thecontrol ofsaid preconditioned means. a V

9. In a machine having a reciprocable carriage, a positive mechanicalstop for limiting movement of the carriage in one direction and meansfor driving the carriage at feed and traverse :rates including a firstreversible electric motor, a second reversible electric motor, aplanetary gear system operatively interposed. between the motors and thecarriage to drive the carriage at a feed rate when only the first motoris operating and at a traverse rate when the second motor is operating,friction brakemeans for said second motor for preventing rotation ofsaid motor while the carriage is being driven at a feed rate, said brakeincluding an electromagnet coil, a resistance in series therewith and ashunt circuit in cluding a switch connected across said resistance. anelectric control system comprising. means controlling operation of themotors to obtain movement of the carriage in one direction at a traverserate, means operable at a predetermined point in said movement todeenergize said second motor and energize said coil through said shuntcircuit to applysaid brake to stop rotation of said second motor andcause said carriage to moveat a feed rate, means operable during suchfeedmovement for opening said switch to break said shunt circuit forreducing the braking torque to cause the brake to slip'andspermit saidfirst motor to drive the second motor when said carriage engages thestop, the reduced torque being high enough to prevent the first motor Ifrom driving the second motor before the, carriage engages the stop,means operable as the carriage approachesthelimit of its movement in theone direction to precondition the controlling means for reverse movementof the carriage while maintaining movement inthe firstidirection, andtiming means-initiating drive of the carriage in the opposite directionunder the control of said preconditioned means. j :9,; Apparatus of; thecharacter claimed inclaim 9, wherein said resistance is variable forreadily adjusting the reduced torque to:v a value where it prevents thefirst motor from "driving the second motor before the carriage "engagesthe stop. 11. In a machine having a reciprocable carriage, a positivemechanical stop for limiting movement of the carriage in one directionand means for driving the carriage at feed and traverse rates includinga first reversible electric motor, a second reversible electric motor, aplanetary gear system operatively interposed between the motors and thecarriage to drive the carriage at a feed rate when only the first motoris operating and at a traverse rate when the second motor is operating,friction brake means for said second motor for preventing rotation ofthe second motor while the carria e is being driven at a feed rate, saidbrake including an electromagnet coil, an electric controlsystemcomprising means controlling operation of the motors to obtain movementof the carriage in one direction at a traverse rate, means operable at apredetermined point in said movement to deenergize said second motor andenergize said coil to apply said brake to cause said carriage to move ata feed rate, means operable during such feed movement for reducing the"braking torque without .deenrgiz ins said. c'oilto" cause the brake to'siioand permit said first 'inotor to driveith-e second motor whensaidioarriage engages the stop,the reduced torque beingrhigh-enough toprevent-'the firsttmotor from driiving the; second 'inotor .beiorethc"carriage engages :the'stop, means operable as the carriage aproaohesthe limit of its movement in the one direction to precondition thecontrolling means ior reverse movement of'thie carriage while main-:tainingmovement in the first direction, and timing rrreanstinitiatingfdrive of the carriage in the opposite direotion undcr'the control orsaid preconditioned means v '12. lria machine having anmovabl'ecarriage,a positive mechanical stop for limiting movement Iii-the carriage in onedirection and meahs'for driving the carriage at feed and traverse ratesincluding a first-"electric motor, a second electric motor, differentialdrive means operatively interposedtoetween the motors and the carriageto drive'the cari'ria'ge at a feedrate when only the first :motor isvogrerafting and :at a tiaverso rate whenithesecondmotor is operating,ririctionibrake means forsaidsecond motor including anelectromagnet'coil, anle'lectriccontrol system comprising meanscontrollingioperation of the motors to ob tam-movement or the carriagein one direction at a traverse'rate, means operable at a'prede terminsd:point in said moven'ient to "deen'ergize saidhrakeito stop rotation ofsaid second motor and oatzsesaid carriage to movea't a rose rate,and-means operable during such iced movement for reducing the.irictionai brakin torque :by

reducing voltageacross said coil withontdeenergizing said coil to causethe brake to slip and ierniit said'nrst motor to drive 9116 second motorwhen said carriage engages the stop, the reduced" torque being high.enough to prevent the fiI'Stfi1(fiOIfrfim-fil ivil'lg the second motorbefore the 1 carriage engages the stop.

1-3. in a machine having a movable carriage, a positive. mechanicalsto'p -for'1imitin movement oi the carriag'e in one direction and meansfor drivingthe carriage at feed and traverse rates including anrstelectric motor, a second-electric motor, differentialdriveih'eansoperativei internosed between the motors and the carriage,to drive the carriage at a Ifeed rate when "only the wfirst motor isoperating and at a traverse rate when the second motor :is operating,friction brake "means for :said second. motor, an electric 24 controlvsystem comprising means controlling oneration'ofthe motors to obtainmovement of the carriage :in onedirection at a traverse rate, meansoperable .at 'a'predeterinined point in said \mQVfiTRGYLt'tOdeenergizesaid second motor and -a;ppiy said brake :tostop rotation ofsaid second motor and cause said carriage to move at :a feed rate,and-.zmeans operable during such feedmove- .for reducing the frictionalbraking torque without reieasing the friction brake to cause the braketo slip and permit said first :niotor to drive the'secondzmotorwhen-said carriage engages the stemtheireduced torque being readilyadjustable $03. vaiuewhere prevents the first motor from driving-thesecond motor before "the carriage engages the stop.

"14. Ina machine having a movable carriage, a positive mechanical stopfor limiting movement of "the carriage in one direction and means fordriving the carriage at feed and traverse rates includingza firstelectric motor, a second electric motor, means operatively interposedbetween-the motors and the carriage to drive the carriage at a iced ratewhen only the 'firstimotor is operating and'at'a'traverse rate when thesecond motor is operating, frictionbrakemeans'for said second motor iforholding :said motor against rotation Wniierthe carriage 'is being drivenat a feed rate, an o. trio control'systemicomprising means cohtrdliing'operation ofthe motors to obtain movenz'eritioithe carriageiin onedirection at a traverse ratepn'ieans operable at a predetermined pointin said movement to deenergize said second motor and 'applyrsaidibraketo cause said carriage to 'moveat a feed rate; and means operableduring" soc, 'ieedmovement ,for reducing the Erictionalrshraking torquewithout releasing the frictionbraire to oausethe :braketo slip andpermit first motor to drive the second motor-when said carriage engagesthe stop, the reduced torque being high enough to revent the firstmotor-from 'drivingthe second motor before the carriage engages thestop.

BENGT R. GRANBERG. .ZBERTIL T. ANDERSON.

REFERENCES CITED The foilowing'refercnces are of record inthe fileofthis patent:

UNITED STATES PATENTS & Number Name Date $398,346 Anderson Apr. .16,194.6

